Bimodal response strategy in Daphnia to ambush predation risk.

Predation's consequences can manifest through either consumptive or nonconsumptive effects, but the prey response may also vary depending on the predator hunting strategy. Considerable attention has been paid to coursing predators, whereas less information is available regarding responses to ambush predators. To remedy this paucity, we utilized a three-dimensional tracking platform to record groups of Daphnia magna under predation risk from the ambush invertebrate predator red-eyed damselfly, Erythromma najas. This design allowed us to test individual antipredator responses in multiple metrics of swimming behaviors. We demonstrate that predation risk was greatest for those that swam at 85% of the available depth and averaged 8.1 mm/s. Examining the swimming behavior of each individual separately showed that predation risk did not affect any of the prey response metrics. Interestingly, however, Daphnia did conform to one of two strategies while under predation risk: either swim fast high up in the water column or swim slowly close to the bottom. Hence, this dichotomous behavior is driven by strategies combining speed and depth in different constellations. In a broader context, our findings highlight the importance of considering both the spatial and temporal dimensions of predation events in order to correctly detect antipredator responses.

2,8-Disubstituted-1,5-naphthyridines as Dual Inhibitors of Plasmodium falciparum Phosphatidylinositol-4-kinase and Hemozoin Formation with In Vivo Efficacy.

Structure-activity relationship studies of 2,8-disubstituted-1,5-naphthyridines, previously reported as potent inhibitors of Plasmodium falciparum (Pf) phosphatidylinositol-4-kinase ß (PI4K), identified 1,5-naphthyridines with basic groups at 8-position, which retained Plasmodium PI4K inhibitory activity but switched primary mode of action to the host hemoglobin degradation pathway through inhibition of hemozoin formation. These compounds showed minimal off-target inhibitory activity against the human phosphoinositide kinases and MINK1 and MAP4K kinases, which were associated with the teratogenicity and testicular toxicity observed in rats for the PfPI4K inhibitor clinical candidate MMV390048. A representative compound from the series retained activity against field isolates and lab-raised drug-resistant strains of Pf. It was efficacious in the humanized NSG mouse malaria infection model at a single oral dose of 32 mg/kg. This compound was nonteratogenic in the zebrafish embryo model of teratogenicity and has a low predicted human dose, indicating that this series has the potential to deliver a preclinical candidate for malaria.

Acute response to pathogens in the early human placenta at single-cell resolution.

The placenta is a selective maternal-fetal barrier that provides nourishment and protection from infections. However, certain pathogens can attach to and even cross the placenta, causing pregnancy complications with potential lifelong impacts on the child's health. Here, we profiled at the single-cell level the placental responses to three pathogens associated with intrauterine complications-Plasmodium falciparum, Listeria monocytogenes, and Toxoplasma gondii. We found that upon exposure to the pathogens, all placental lineages trigger inflammatory responses that may compromise placental function. Additionally, we characterized the responses of fetal macrophages known as Hofbauer cells (HBCs) to each pathogen and propose that they are the probable niche for T. gondii. Finally, we revealed how P. falciparum adapts to the placental microenvironment by modulating protein export into the host erythrocyte and nutrient uptake pathways. Altogether, we have defined the cellular networks and signaling pathways mediating acute placental inflammatory responses that could contribute to pregnancy complications.

Prediction model to identify infectious COVID-19 patients in the emergency department.

Background: Real-time reverse-transcriptase polymerase chain reaction (RT-PCR) has been the gold standard for diagnosing coronavirus disease 2019 (COVID-19) but has a lag time for the results. An effective prediction algorithm for infectious COVID-19, utilized at the emergency department (ED), may reduce the risk of healthcare-associated COVID-19. Objective: To develop a prototypic prediction model for infectious COVID-19 at the time of presentation to the ED. Material and methods: Retrospective cohort study of all adult patients admitted to Singapore General Hospital (SGH) through ED between March 15, 2020, and December 31, 2022, with admission of COVID-19 RT-PCR results. Two prediction models were developed and evaluated using area under the curve (AUC) of receiver operating characteristics (ROC) to identify infectious COVID-19 patients (cycle threshold (Ct) of <25). Results: Total of 78,687 patients were admitted to SGH through ED during study period. 6,132 of them tested severe acute respiratory coronavirus 2 positive on RT-PCR. Nearly 70% (4,226 of 6,132) of the patients had infectious COVID-19 (Ct<25). Model that included demographics, clinical history, symptom and laboratory variables had AUROC of 0.85 with sensitivity and specificity of 80.0% & 72.1% respectively. When antigen rapid test results at ED were available and added to the model for a subset of the study population, AUROC reached 0.97 with sensitivity and specificity of 95.0% and 92.8% respectively. Both models maintained respective sensitivity and specificity results when applied to validation data. Conclusion: Clinical predictive models based on available information at ED can be utilized for identification of infectious COVID-19 patients and may enhance infection prevention efforts.

Quinoxaline-Based Anti-Schistosomal Compounds Have Potent Anti-Malarial Activity.

The human pathogens Plasmodium and Schistosoma are each responsible for over 200 million infections annually, being particularly problematic in low- and middle-income countries. There is a pressing need for new drug targets for these diseases, driven by emergence of drug-resistance in Plasmodium and the overall dearth of new drug targets for Schistosoma. Here, we explored the opportunity for pathogen-hopping by evaluating a series of quinoxaline-based anti-schistosomal compounds for activity against P. falciparum. We identified compounds with low nanomolar potency against 3D7 and multidrug-resistant strains. Evolution of resistance using a mutator P. falciparum line revealed a low propensity for resistance. Only one of the series, compound 22, yielded resistance mutations, including point mutations in a non-essential putative hydrolase pfqrp1, as well as copy-number amplification of a phospholipid-translocating ATPase, pfatp2, a potential target. Notably, independently generated CRISPR-edited mutants in pfqrp1 also showed resistance to compound 22 and a related analogue. Moreover, previous lines with pfatp2 copy-number variations were similarly less susceptible to challenge with the new compounds. Finally, we examined whether the predicted hydrolase activity of PfQRP1 underlies its mechanism of resistance, showing that both mutation of the putative catalytic triad and a more severe loss of function mutation elicited resistance. Collectively, we describe a compound series with potent activity against two important pathogens and their potential target in P. falciparum.

hERG, Plasmodium Life Cycle, and Cross Resistance Profiling of New Azabenzimidazole Analogues of Astemizole.

Toward addressing the cardiotoxicity liability associated with the antimalarial drug astemizole (AST, hERG IC50 = 0.0042 µM) and its derivatives, we designed and synthesized analogues based on compound 1 (Pf NF54 IC50 = 0.012 µM; hERG IC50 = 0.63 µM), our previously identified 3-trifluoromethyl-1,2,4-oxadiazole AST analogue. Compound 11 retained in vitro multistage antiplasmodium activity (ABS PfNF54 IC50 = 0.017 µM; gametocytes PfiGc/PfLGc IC50 = 1.24/1.39 µM, and liver-stage PbHepG2 IC50 = 2.30 µM), good microsomal metabolic stability (MLM CLint < 11 µL·min-1·mg-1, EH < 0.33), and solubility (150 µM). It shows a ∼6-fold and >6000-fold higher selectivity against human ether-á-go-go-related gene higher selectively potential over hERG relative to 1 and AST, respectively. Despite the excellent in vitro antiplasmodium activity profile, in vivo efficacy in the Plasmodium berghei mouse infection model was diminished, attributable to suboptimal oral bioavailability (F = 14.9%) at 10 mg·kg-1 resulting from poor permeability (log D7.4 = -0.82). No cross-resistance was observed against 44 common Pf mutant lines, suggesting activity via a novel mechanism of action.

Reaction hijacking inhibition of Plasmodium falciparum asparagine tRNA synthetase.

Malaria poses an enormous threat to human health. With ever increasing resistance to currently deployed drugs, breakthrough compounds with novel mechanisms of action are urgently needed. Here, we explore pyrimidine-based sulfonamides as a new low molecular weight inhibitor class with drug-like physical parameters and a synthetically accessible scaffold. We show that the exemplar, OSM-S-106, has potent activity against parasite cultures, low mammalian cell toxicity and low propensity for resistance development. In vitro evolution of resistance using a slow ramp-up approach pointed to the Plasmodium falciparum cytoplasmic asparaginyl-tRNA synthetase (PfAsnRS) as the target, consistent with our finding that OSM-S-106 inhibits protein translation and activates the amino acid starvation response. Targeted mass spectrometry confirms that OSM-S-106 is a pro-inhibitor and that inhibition of PfAsnRS occurs via enzyme-mediated production of an Asn-OSM-S-106 adduct. Human AsnRS is much less susceptible to this reaction hijacking mechanism. X-ray crystallographic studies of human AsnRS in complex with inhibitor adducts and docking of pro-inhibitors into a model of Asn-tRNA-bound PfAsnRS provide insights into the structure-activity relationship and the selectivity mechanism.

Propensity of selecting mutant parasites for the antimalarial drug cabamiquine.

We report an analysis of the propensity of the antimalarial agent cabamiquine, a Plasmodium-specific eukaryotic elongation factor 2 inhibitor, to select for resistant Plasmodium falciparum parasites. Through in vitro studies of laboratory strains and clinical isolates, a humanized mouse model, and volunteer infection studies, we identified resistance-associated mutations at 11 amino acid positions. Of these, six (55%) were present in more than one infection model, indicating translatability across models. Mathematical modelling suggested that resistant mutants were likely pre-existent at the time of drug exposure across studies. Here, we estimated a wide range of frequencies of resistant mutants across the different infection models, much of which can be attributed to stochastic differences resulting from experimental design choices. Structural modelling implicates binding of cabamiquine to a shallow mRNA binding site adjacent to two of the most frequently identified resistance mutations.

Reaction hijacking inhibition of Plasmodium falciparum asparagine tRNA synthetase.

Malaria poses an enormous threat to human health. With ever increasing resistance to currently deployed drugs, breakthrough compounds with novel mechanisms of action are urgently needed. Here, we explore pyrimidine-based sulfonamides as a new low molecular weight inhibitor class with drug-like physical parameters and a synthetically accessible scaffold. We show that the exemplar, OSM-S-106, has potent activity against parasite cultures, low mammalian cell toxicity and low propensity for resistance development. In vitro evolution of resistance using a slow ramp-up approach pointed to the Plasmodium falciparum cytoplasmic asparaginyl tRNA synthetase (PfAsnRS) as the target, consistent with our finding that OSM-S-106 inhibits protein translation and activates the amino acid starvation response. Targeted mass spectrometry confirms that OSM-S-106 is a pro-inhibitor and that inhibition of PfAsnRS occurs via enzyme-mediated production of an Asn-OSM-S-106 adduct. Human AsnRS is much less susceptible to this reaction hijacking mechanism. X-ray crystallographic studies of human AsnRS in complex with inhibitor adducts and docking of pro-inhibitors into a model of Asn-tRNA-bound PfAsnRS provide insights into the structure activity relationship and the selectivity mechanism.

Activity of Ivermectin and Its Metabolites against Asexual Blood Stage Plasmodium falciparum and Its Interactions with Antimalarial Drugs.

Ivermectin is an endectocide used widely to treat a variety of internal and external parasites. Field trials of ivermectin mass drug administration for malaria transmission control have demonstrated a reduction of Anopheles mosquito survival and human malaria incidence. Ivermectin will mostly be deployed together with artemisinin-based combination therapies (ACT), the first-line treatment of falciparum malaria. It has not been well established if ivermectin has activity against asexual stage Plasmodium falciparum or if it interacts with the parasiticidal activity of other antimalarial drugs. This study evaluated antimalarial activity of ivermectin and its metabolites in artemisinin-sensitive and artemisinin-resistant P. falciparum isolates and assessed in vitro drug-drug interaction with artemisinins and its partner drugs. The concentration of ivermectin causing half of the maximum inhibitory activity (IC50) on parasite survival was 0.81 µM with no significant difference between artemisinin-sensitive and artemisinin-resistant isolates (P = 0.574). The ivermectin metabolites were 2-fold to 4-fold less active than the ivermectin parent compound (P < 0.001). Potential pharmacodynamic drug-drug interactions of ivermectin with artemisinins, ACT-partner drugs, and atovaquone were studied in vitro using mixture assays providing isobolograms and derived fractional inhibitory concentrations. There were no synergistic or antagonistic pharmacodynamic interactions when combining ivermectin and antimalarial drugs. In conclusion, ivermectin does not have clinically relevant activity against the asexual blood stages of P. falciparum. It also does not affect the in vitro antimalarial activity of artemisinins or ACT-partner drugs against asexual blood stages of P. falciparum.

Generation of a mutator parasite to drive resistome discovery in Plasmodium falciparum.

In vitro evolution of drug resistance is a powerful approach for identifying antimalarial targets, however, key obstacles to eliciting resistance are the parasite inoculum size and mutation rate. Here we sought to increase parasite genetic diversity to potentiate resistance selections by editing catalytic residues of Plasmodium falciparum DNA polymerase δ. Mutation accumulation assays reveal a ~5-8 fold elevation in the mutation rate, with an increase of 13-28 fold in drug-pressured lines. Upon challenge with the spiroindolone PfATP4-inhibitor KAE609, high-level resistance is obtained more rapidly and at lower inocula than wild-type parasites. Selections also yield mutants with resistance to an "irresistible" compound, MMV665794 that failed to yield resistance with other strains. We validate mutations in a previously uncharacterised gene, PF3D7_1359900, which we term quinoxaline resistance protein (QRP1), as causal for resistance to MMV665794 and a panel of quinoxaline analogues. The increased genetic repertoire available to this "mutator" parasite can be leveraged to drive P. falciparum resistome discovery.

Advances in malaria pharmacology and the online guide to MALARIA PHARMACOLOGY: IUPHAR review 38.

Antimalarial drug discovery has until recently been driven by high-throughput phenotypic cellular screening, allowing millions of compounds to be assayed and delivering clinical drug candidates. In this review, we will focus on target-based approaches, describing recent advances in our understanding of druggable targets in the malaria parasite. Targeting multiple stages of the Plasmodium lifecycle, rather than just the clinically symptomatic asexual blood stage, has become a requirement for new antimalarial medicines, and we link pharmacological data clearly to the parasite stages to which it applies. Finally, we highlight the IUPHAR/MMV Guide to MALARIA PHARMACOLOGY, a web resource developed for the malaria research community that provides open and optimized access to published data on malaria pharmacology.

Spontaneous Tumor Lysis Syndrome in a Patient With a Known History of Chronic Lymphocytic Leukemia Prior to Cytotoxic Chemotherapy.

Tumor lysis syndrome (TLS) is an oncological emergency resulting in an imbalance of electrolytes released upon tumor cell death leading to life-threatening acute renal failure. Typically, TLS is triggered by cytotoxic chemotherapy; however, it can rarely occur spontaneously. Our case report presents a patient with a known malignancy, but not on any cytotoxic chemotherapy, who presents to the emergency department with metabolic derangements suggestive of spontaneous TLS. Our case highlights the importance of considering an uncommon manifestation of TLS despite the absence of cytotoxic chemotherapy. This case is unique as it demonstrates the manifestations of TLS in a patient with a known stable malignancy and discusses the subsequent management.

Managing painful shoulder after neurological injury.

Shoulder pain is common after neurological injury and can be disabling, lead to poor functional outcomes and increase care costs. Its cause is multifactoral and several pathologies contribute to the presentation. Astute diagnostic skills and a multidisciplinary approach are required to recognise what is clinically relevant and to implement appropriate stepwise management. In the absence of large clinical trial data, we aim to provide a comprehensive, practical and pragmatic overview of shoulder pain in patients with neurological conditions. We use available evidence to produce a management guideline, taking into account specialty opinions from neurology, rehabilitation medicine, orthopaedics and physiotherapy.

Cytoplasmic isoleucyl tRNA synthetase as an attractive multistage antimalarial drug target.

Development of antimalarial compounds into clinical candidates remains costly and arduous without detailed knowledge of the target. As resistance increases and treatment options at various stages of disease are limited, it is critical to identify multistage drug targets that are readily interrogated in biochemical assays. Whole-genome sequencing of 18 parasite clones evolved using thienopyrimidine compounds with submicromolar, rapid-killing, pan-life cycle antiparasitic activity showed that all had acquired mutations in the P. falciparum cytoplasmic isoleucyl tRNA synthetase (cIRS). Engineering two of the mutations into drug-naïve parasites recapitulated the resistance phenotype, and parasites with conditional knockdowns of cIRS became hypersensitive to two thienopyrimidines. Purified recombinant P. vivax cIRS inhibition, cross-resistance, and biochemical assays indicated a noncompetitive, allosteric binding site that is distinct from that of known cIRS inhibitors mupirocin and reveromycin A. Our data show that Plasmodium cIRS is an important chemically and genetically validated target for next-generation medicines for malaria.

The Association Between Functional Movement Screen Scores and Knee Valgus Moments During Unplanned Sidestep Cutting in Netball.

Background: Regular employment of three-dimensional (3D) motion analyses to assess and monitor knee valgus moments; a contributor to non-contact anterior cruciate ligament (ACL) injury; during unplanned sidestep cutting (USC) is costly and time-consuming. An alternative quick-to-administer assessment tool to infer an athlete's risk for this injury could allow prompt and targeted interventions to mitigate this risk. Purpose: This study investigated whether peak knee valgus moments (KVM) during weight-acceptance phase of an unplanned sidestep cut were correlated with composite and component scores of the Functional Movement Screen (FMS™). Study Design: Cross-sectional, Correlation. Methods: Thirteen female national-level netballers performed six movements of the FMS™ protocol and three trials of USC. A 3D motion analysis system captured lower limb kinetics and kinematics of each participant's non-dominant leg during USC. Averages of peak KVM across USC trials were calculated and examined for correlations with composite and component scores of the FMS™. Results: No correlations were found between FMS™ composite or any of its component scores with peak KVM during USC. Conclusions: The current FMS™ did not show any correlations with peak KVM during USC on the non-dominant leg. This suggests that the FMS™ has limited utility in screening for non-contact ACL injury risks during USC. Level of Evidence: 3.

Does the surgical treatment of concomitant upper limb fractures affect the outcomes of hip fractures in the elderly population?

INTRODUCTION: Elderly patients with concomitant upper limb and hip fractures present a management dilemma because upper limb fractures potentially affect rehabilitation outcomes for the hip fracture. This study aims to evaluate whether the site of upper limb fractures and the decision to surgically treat such fractures affect the functional outcome of surgically treated hip fracture patients. METHODOLOGY: We retrospectively reviewed 1828 hip fracture patients treated at a single trauma centre over 3 years, of whom 42 with surgically treated hip fractures had concomitant upper limb fractures. Outcome measures, such as length of hospital stay, complications, mortality and readmission rates, were assessed, whilst the functional outcomes were evaluated using the Modified Barthel Index (MBI) on admission, post-operatively and at 6 and 12 months of follow-up. RESULTS: Amongst the 42 patients with surgically treated hip fractures, 31.0% had proximal humerus fractures, 50.0% had wrist fractures, 16.7% had elbow fractures and 2.4% had forearm fractures. 50.0% of these upper limb fractures were treated surgically. There was no difference in complications, inpatient morbidity, readmission rates or the length of hospital stay for patients whose upper limb fractures were surgically treated as compared to those non-surgically treated. There was no difference in absolute MBI scores at 6 and 12 months based on the management of upper limb fractures. However, patients with surgically treated wrist fractures had statistically significant higher MBI scores at 6 months as compared to those treated non-surgically. CONCLUSION: Surgical treatment of concomitant upper limb fractures does not appear to change the outcomes of the hip fractures. Hip fracture patients with surgically treated wrist fractures had better functional outcomes at 6 months compared to those treated non-surgically; however, there was no difference at 12 months. Hip fracture patients with concomitant wrist fractures had better functional outcomes compared to hip fracture patients with proximal humerus fractures.